Planographic printing plate and method of preparing the same



Patented Feb. 20, 1951 PLANOGRAPHIC PRINTING PLATE AND METHOD OF PREPARING THE SAME Charles H. Van Dusen, Jr.,

Willoughby, Ohio, as-

signor to Addressograph-Multigraph Corporaa corporation of Delaware No Drawing. Application September 21, 1945, Serial No. 817,916

11 Claims. (o1. ion-149.2)

tion, Cleveland, Ohio,

This invention relates to cellulose base pianographic printing plates and to a method of making such planographic printing plates. More particularly, this invention relates to cellulose base planographic printing plates of the type which may be employed as master planographic printing plates upon rotary oflset planographic printing presses and thelike.

Among the difiiculties experienced heretofore in connection with certain cellulose base planographic printing plates has been the tendency of such plates to curl when stored between successive uses thereof. This is particularly objectionable in view of the fact that such plates are commonly used in business oflices and like places and must be stored in flat form for considerable periods of time between successive uses thereof.

Moreover, the printing surface or surfaces of a cellulose base planographic plate must afford a flexible, water-insoluble, ink-receptive hydrophilic surface which is resistant to the action of common solvents and to fingerprints and the like, is receptive to fatty or reasy and non-greasy lithographic inks and like lithographic materials and yet is capable of being rendered repellent to fatty or greasy as well as non-greasy lithographic printing inks by means of aqueous lithographic repellent solutions. At the same time the cellulose base or backing in such a planographic printing plate must possess dimensional stability and high wet strength in the presence of water due to the fact that it comes into contact with aqueous lithographic repellent solutions in use. Such plates must, moreover, possess good reproduction characteristics including the ability to afford good copies and relatively large or long editions thereof.

In the present invention I have found that certain salts of carboxy methyl cellulose or cellulose glycollic acid and the reaction products of some of such salts with certain modifying agents afford firmly adhering, tough, flexible films which aflord good hydrophilic planographic surfaces upon cellulose base sheets or backings having the desirable properties and characteristics herein.

a before pointed out and others which are inherent therein.

Accordingly, an object of the present invention is to afford a cellulose base planographic printing plate having a new and improved planographic printing surface which has the desirable advantages, properties and characteristics hereinbefore pointed out and others which are inherent therein.

2 novel method of preparing the new cellulose base planographic printing plate.

Other and further objects of the present invention will be apparent from the following description and claims which, by way of illustration, show preferred embodiments and the principles thereof and what I now consider to be the best modes in which I have contemplated applying those principles. Other embodiments of the invention embodying the same or equivalent principles may be used and changes may be made as desired by those skilled in the art without departin from the present invention and the purview of the appended claims.

In the practice of the present invention I may employ as a backing sheet or base a dimensionally stable high wet strength sheet such as a cellulose or paper base sheet containing a melamine resin or a resin of the urea-formaldehyde type, or like cellulose sheet possessed of suitable wet strength and dimensional stability. Thus a suitable paper for use in making the new planographic printing plates may be, for example, a good grade of high wet strength map paper such, for example, as that which is described in United States Patents Nos. 2,134,165 and 2,205,998. The cellulose base or backing sheet may, of course, be cut to proper planographic printing plate size either before or after it has been provided with the new planographic printing surface and which may be afforded in a manner which will now be described.

In the practice of the present invention I may employ as the base of the coating solution to be applied to the cellulose backing sheet or base any one of certain selected salts of carboxy methyl cellulose or cellulose glycollic acid, includin the water-soluble sodium salt and the water-insoluble aluminum, barium, stannous tin, lead, and ferrous and ferric salts of said acid.

Thus a suitable formula which may be followed in preparing a coating composition for a. parchment or like cellulose backing sheet in the practice of the present invention is shown in the following example:

' solution of the sodium salt of carboxy methyl Another object of the invention is to afford a ll cellulose (2%) is mixed with an equal volume of a ten percent phosphoric acid (HaPO4) solution and to the mixture thus formed there was added finely divided hydrated alumina (AlzOaxl-ho) in a quantity equal to 30 percent of the weight of the mixture of the sodium salt of carboxy methyl cellulose and phosphoric acid (HsPOs).

ner as, for example, by coating, spraying, brushing, or otherwise. One product of the reaction of the water-soluble sodium cellulose glycollate and phosphoric acid is insoluble cellulose glycollic acid and when a cellulose base sheet coated therewith is dried, it forms a flrmly adhering, tough flexible fllm thereon.

In place of the phosphoric acid specified in the foregoing Example 1, hydrochloric acid may also be used, although phosphoric acid is preferred thereover since the hydrochloric acid tends to attack the paper sheet'when the composition is applied thereto.

The hydrated alumina (AlzOaXHzO) which is incorporated in the coating composition referred to in the foregoing Example 1 serves primarily as a flller, giving bulk to the coating composition. It also imparts a certain degree of hardness or roughness to the resulting sheet coated therewith and thus affords a roughened surface to which the image-forming material may anchor itself when an image is inscribed upon the thus coated sheet.

A cellulose backing sheet thus coated with the coating composition referred to in the foregoing Example 1 may be dried by being exposed to infra-red light for a suiflcient length of time or by allowing it to dry at atmospheric temperature. The result is a cellulose base planographic printing plate coated with a hydro- I coated and dried master plate by means of various, known lithographic writing or image-forming mediaincluding lithographic typewriter rib- I bon, lithographic crayon, and lithographic writing fluid of both the greasy and non-greasy image-formin types, whereupon the plates may be employed in a rotary offset lithographic printing press so as to form images or reproductions upon paper sheets run through the press, employing aqueous repellent solutions, in a manner well understood in the art. The cellulose base planographic printing plates thus prepared exhibit substantially no tendency to curl either when wet or dry or when dried after use, possess good dimensional stability or resistance to swelling after contact with aqueous pianographic printing solutions, and afford satisfactory copies or reproductions which are particularly good in those instances in which the inscriptions upon the master plate are made with lithographic crayon. 1

Another formula which may be followed in preparing a coating composition which may be used for forming a lithographic surface upon a cellulose base or backing sheet, in the practice of the present invention, is shown in the following example:

- Example 2 7 Parts, grams (1) High viscosity aluminum salt of carboxy methyl cellulose (1%) 30 (2) NHiOH (28%) 10.44 (3) Hydrated alumina (AlzOa.XH20) (finely divided) 12.0

In preparing the coating composition set forth aluminum cellulose glycollate ("Collocell A," high viscosity. Dow Chemical Co.) are stirred with the 10.44 grams of NH4OH (28%) and the 1500 c. c. of distilled water until the mixture forms a thin jelly-like material. A quantity of this material is then placed in a mortar and to it is added approximately 30% of its weight of the flller or hydrated alumina (A1203.XH2O), whereupon the mixture is worked in the mortar to a smooth paste. The resulting composition is then ready for application to the paper base sheet upon which it may be spread in any suitable manner to a thickness suflicient completely to cover the surface of the paper base sheet. The thus coated paper base sheet may then be heated and dried by exposure to infra-red light for a length of time suilicient to drive off all of the ammonia (NHa). The thus prepared paper base planographic printing plate is then ready for use.

Unlike the aforesaid sodium salt, the aluminum salt of carboxy methyl cellulose, or aluminum cellulose glycollate, referred to in the foregoing Example 2, is insoluble in water but is soluble in aqueous ammonia or NHiOH solution. Hence a cellulose base or backing sheet coated with an aqueous ammonia solution of aluminum cellulose glycollate affords a surface which is receptive to image-forming compositions, if the thus coated sheet is heated sufllciently to drive off substantially all of the ammonia, thereby precipitating water-insoluble aluminum cellulose glycollate upon the cellulose base sheet. Thus it will be seen that the coating composition referred to in the foregoing Example 2 is in some respects preferable to that which is set forth in Example 1.

In the practice of the present invention the cellulose base or backing sheet may, of. course, be

coated on one or both sides with a selected one of the aforesaid coating compositions, as desired.

It may be desirable, in certain instances, to incorporate with the coating composition, such as those which are described in the foregoing examples. other hydrophilic modifying agents such, for example, as a plasticizer which may be, for example, polyamyl alcohol, melamine-formaldehyde resin, or a urea-formaldehyde resin for the purpose of improving the flexibility of the resulting film and coated sheet. Moreover, I may incorporate in the coating solution one or more additional selected fillers to improve the adherence or anchoring of the resulting film upon the cellulose base sheet and among such additional flllers which may be used are china clay, titanium dioxide, calcium carbonate, barium sulphate (blanc flxe), fluorspar, fullers earth, and others. It will be noted, in this connection, that the hydrated alumina recited in the foregoing examples also functions as a flller and as a roughnessimparting material.

It will thus be seen that the present invention affords a new and improved cellulose base planographic printing plate having thereon a tough, firmly adhering, flexible, water-insoluble, hydrophilic planographic surface which is receptive to image-forming compositions, said surface being afforded by the water-insoluble reaction product of a water-soluble salt of carboxy methyl cellulose, and an insolubilizing agent, such as phosphoric acid, together with a filler and roughnessimparting substance, such as hydrated alumina, (Al2Os.XHz0) or by a water-insoluble salt of said acid, such as the aluminum salt thereof, with or without One or more additional selected fillers as set forth above, for improving the adherence or anchoring of the resulting film to its underlying and supporting cellulose base sheet.

Among the advantages of the new coated paper base planographic printing plate thus prepared is that it is economical in manufacture, does not curl upon standing between successive uses, has good dimensionally stable high wet strength, does not cause the image thereon to spread upon running editions therefrom, and may be employed with a wide variety of imageforming compositions including those of both the greasy and non-greasy types.

It will thus be seen that the present invention affords a novel coated cellulose base planographic printing plate having the aforesaid desirable properties and characteristics, and thus accomplishes its intended objects, including those hereinbefore pointed out, and others which are inherent in the invention.

It will also thus be seen that the present invention affords a. novel method of preparing the new coated cellulose base planographic printing plates, and thus accomplishes the intended objects of the method hereinbefore disclosed, including those hereinbefore specifically pointed out, and others which are inherent in the invention.

I claim:

1. A planographic printing plate comprising a cellulose base sheet having thereon a tough, fiexible coating of carboxy methyl cellulose, said coating providing a hydrophilic surface which is receptive to lithographic image-forming materials, and an ink-receptive water-repellent image on the surface of said coating.

2. A planographic printing plate comprising a cellulose base sheet having thereon a tough, flexible firmly adhering coating of cellulose glycollic acid. said coating providing a hydrophilic surface which is receptive to lithographic imageforming materials, and an ink-receptive waterrepellent image on the surface of said coating.

3. A planographic printing plate comprising a cellulose base sheet having thereon a tough, flexible, firmly-adhering coating comprised of the water-insoluble reaction product of a watersoluble salt of carboxy methyl cellulose and an acid, said coating providing a hydrophilic surface which, is receptive to lithographic image-forming materials, and an ink-receptive water-repellent image on the surface of said coating.

4. A planographic printing plate comprising a cellulose base sheet having thereon a tough, flexible, firmly-adhering coating comprised of the water-insoluble reaction product of the sodium salt of cellulose glycollic acid and phosphoric acid, said coating providing a hydrophilic surface which is receptive to lithographic imageforming materials, and an ink-receptive waterrepellent image on the surface of said coating.

5. A planographic printing plate comprising a cellulose base sheet having thereon a tough, flexible, firmly-adhering coating comprised of the water-insoluble reaction product of the sodium salt of cellulose glycollic acid and phosphoric acid, and a mineral filler, said coating providing a hydrophilic surface which is receptive to lithographic image-forming materials, and an inkreceptive water-repellent image on the surface of said coating.

6. A planographic printing plate as defined in claim 5 in which the mineral filler is .hydrated alumina.

7. A planographic printing plate comprising a cellulose base sheet having thereon a tough, flexible, firmly-adhering coating comprised of the water-insoluble aluminum salt of carboxy methyl cellulose and a volatile solvent for said waterinsoluble salt, said coating providing a hydrophilic surface which is receptive to lithographic image-forming materi s, and an ink-receptive water-repellent image on the surface of said coating.

8. A planographic printing plate as defined in claim 7 in which the volatile solvent for the water-insoluble aluminum salt of carboxy methyl cellulose is ammonium hydroxide.

9. A planographic printing plate as defined in claim '7 in which the said coating includes a mineral filler.

10. A planographic printing plate as defined in claim 7 in which the said coating includes hydrated alumina.

11. A planographic printing plate comprising a foundation, and a film on the surface of said foundation containing a carboxymethyl cellulose compound as the essential film-forming component thereof, said film being grease-and-waterreceptive when dry and grease-repellent when wet, and an ink-receptive water-repellent image on the surface of said coating.

CHARLES H. VAN DUSEN, JR.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS ware. 

11. A PLANOGRAPHIC PRINTING PLATE COMPRISING A FOUNDATION, AND A FILM ON THE SURFACE OF SAID FOUNDATION CONTAINING A CARBOXYMETHYL CELLULOSE COMPOUND AS THE ESSENTIAL FILM-FORMING COMPONENT THEREOF, SAID FILM BEING GREASE-AND-WATERRECEPTIVE WHEN DRY AND GREASE-REPELLENT WHEN WET, AND AN INK-RECEPTIVE WATER-REPELLENT IMAGE ON THE SURFACE OF SAID COATING. 